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Volcanowatch

November 9, 2000

A weekly feature provided by scientists at the Hawaiian Volcano Observatory.


Thermal Ducks - The new weapon in volcano monitoring?

Anyone who has been close to an active flow or steam vent knows that the heat coming from one of these features is intense and, at times, overwhelming! It will come as no surprise, then, that thermal monitoring of volcanoes and their products plays an important part in volcanology.

Volcanologists are under increasing pressure to develop remote- monitoring techniques and instruments that can provide continuous data in real-time. Near real-time thermal monitoring from satellite sensors is already a reality (for example, see http://virtual1.pgd.hawaii.edu/goes/). In this particular example there is a 12-minute delay as information is transmitted from the satellite, via image-analysis software, to a display on the world- wide web. This kind of thermal remote-monitoring has proven particularly useful in the detection and tracking of events at active volcanoes in remote areas where direct observations are not always possible.

At many volcanoes, such as Kilauea, scientists are often interested in changes in activity that occur over shorter time periods than satellites can detect. In addition, thermal monitoring using satellites suffers from other problems due to poor viewing conditions caused by cloud and fume (common conditions at Pu`u `O`o), which can prevent the detection of important volcanic features, such as glowing vents.

A new venture between the University of Hawai`i at Manoa and the Hawaiian Volcano Observatory (HVO) has resulted in the construction of an expendable, near real-time thermal monitoring system that can be rapidly deployed. The system was installed on the north rim of Pu`u `O`o Crater at the beginning of October 2000 to test its reliability in a harsh, corrosive volcanic environment.

The system consists of three modules: thermal sensors, transmission/power hub, and a reception center. The sensors (Huey, Dewey and Louie) can be pointed at interesting volcanic features in the crater. They are housed in tripod-mounted, gas-resistant casing with special protective viewing windows. These windows allow the sensors to detect radiation in the 8-14 micrometers waveband. Sensing in this waveband enables the detection of thermal radiation through cloud and fume, over a wide temperature range, with minimal signal damping resulting from absorption of the signal by water vapor and other gases in the atmosphere. The signal is affected by the presence of fume and steam, but volcanic hotspots give a sufficient increase in signal to distinguish them from background environmental noise. Signals are sampled and transmitted every two seconds from a radio modem via a repeater site to HVO. Here, three temperature measurements with a time and date stamp are saved to a computer file, and temperatures are graphically displayed in near real-time.

At present, one sensor (Huey) positioned on the rim of Pu`u `O`o looks at a glowing vent in the crater from which we could detect thermal radiation. It was visibly incandescent during our time on the rim but could not be detected by a video camera. Louie looks westward across the crater, in the hope of catching thermal signals resulting from activity in the west gap of the Pu`u `O`o cone. The third sensor (Dewey) is sighted upon our hottest target to date - a vent near the east end of the crater floor.

We hope that the system proves to be robust and reliable, after initial "teething" problems, so that, in the very near future, volcanologists can use it to help their understanding of processes occurring before, during, and after eruptive episodes.

Eruption Update

Eruptive activity of Kilauea Volcano continued unabated during the past week. Lava is erupting from Pu`u `O`o and flowing southeast through a tube system down to the flats below Pulama pali and beyond to the ocean. Lava is entering the ocean at Kamokuna located 1.6 km (1 mi) west-southwest of Waha`ula.

The public is reminded that the ocean-entry areas are extremely hazardous, with explosions accompanying sudden collapses of the new land. The active lava flows are hot and have places with very thin crust. The steam clouds are highly acidic and laced with glass particles. We include this warning with nearly every eruption update to remind visitors of the dangers involved with lava viewing. A detailed explanation of the ocean entry activity and the related hazards can be found on our website (http://hvo.wr.usgs.gov).

There were no earthquakes reported felt during the week ending on November 9.


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Updated: November 14, 2000